Tour de France champion Alberto Contador has scheduled a news conference for Thursday to address reports of an apparent positive test for the bronchodilator clenbuterol.

Contador, a three-time winner of the French national tour, apparently tested positive for the drug in tests conducted on July 21, the second of two rest days in this year’s race and was notified of the result on August 24.

According to a release issued by his publicist, Contador is scheduled to hold a press conference at noon Thursday at the Hotel Las Artes in his hometown of Pinto, Spain. Contador has assembled a group of experts who will contend that the positive test is the result of “food contamination.”

“The experts consulted so far have agreed also that this is a food contamination case, especially considering the number of tests passed by Alberto Contador during the Tour de France,” the release asserted.

Contador said that a review of data supplied by the UCI makes it “possible to define precisely both the time of the emergence of the substance as well as the tiny amount detected, ruling out any other source or intentionality.”

Clenbuterol is a synthetic bronchodilator often prescribed to asthma sufferers. It is also regarded as a stimulant and has recently been used in off-label prescriptions as a weight-loss drug akin to ephedrine. The drug is on the World Anti-Doping Agency’s banned substances list and is specifically banned under Article 21 of the UCI’s anti-doping rules.

Trace amounts still mean provisional suspension

The UCI soon announced that Contador had been provisionally suspended after the news broke at the world road championships in Australia.

The UCI confirmed that the clenbuterol was detected in a urine sample taken from the Spaniard on July 21, the second rest day of the race in Pau at the foot of the French Pyrenees.

But the governing body added that only a “very small concentration” of the drug had been found and that the case warranted “further scientific investigation” because the Cologne laboratory that detected the substance is known to be able to detect the tiniest traces of drugs.

“The rider, who had already put an end to his cycling season before the result was known, was nevertheless formally and provisionally suspended as is prescribed by the World Anti-Doping Code,” a UCI statement said.

“The concentration found by the laboratory was estimated at 50 picograms (50 trillionths of a gram) which is 400 times less than what the antidoping laboratories accredited by WADA (World Anti Doping Agency) must be able to detect,” it said, adding that testing of a second “B” sample taken at the same time confirmed the result.

Food contamination?

Contador, speaking briefly to Spanish radio, denied he had used banned substances.

“You can put your hand in the fire and you won’t get burned,” Contador told COPE radio. “If there had been a clear case of doping, it would have come out in a week. The food poisoning came from eating beef that came from Spain.”

Trace elements of the drug found in the human body can on occasion be attributed to food contamination. If it is found in larger amounts it usually points to deliberate doping.

RadioShack’s Fuyu Li recently was suspended after testing positive for clenbuterol at the 2010 Dwaars Door Vlaanderen in March. Former Tour de France points jersey winner, Djamolidine Abdoujaparov, retired from the sport soon after testing for high levels of clenbuterol during the ’97 Tour.

Contador, however, tested positive for extremely low levels and says that is indicative of exposure to contaminated food and not abuse for purposes of performance enhancement.

Contador’s argument is being vigorously backed up by Dutch anti-doping expert, Douwe de Boer, who said the amount found in his body points “clearly in the direction of a contamination” and that such a low dose would not aid performance. De Boer points out that a series of samples taken both before and after the July 21st positive, suggest that there was only a small level of clenbuterol present in Contador’s system and that peaked on the 21st. De Boer points to the 32-hour half-life of the drug as a strong indication that Contador ingested the drug in a small dose, most likely to be from contaminated food.

Clenbuterol has been used by meat producers as a non-steroidal means of increasing muscle-to-fat ratios, although the method is banned in most countries. There have been several documented cases of food-borne clenbuterol contamination, including in the United States and Europe, although the most notable occurred in China. In the U.S., the only permitted veterinary use of the drug is to address respiratory ailments in horses.

While banned, there has been little history of enforcement and meat producers have been known to use the drug to enhance the production of lean meats.

Tour takes wait-and-see approach

Contador risks becoming only the second rider in the history of the Tour de France to be stripped of his title because of a doping violation. American Floyd Landis was found guilty of a doping violation following the 2006 Tour.

Winner Maurice Garin and the next three finishers were disqualified for non-pharmaceutical infractions in 1904.

Tour de France organizers from the Amaury Sports Organisation said they had learned about the adverse analytical finiding through the UCI’s statement on Thursday morning, but would take no action until further study is conducted.

“The UCI has indicated that further scientific investigation, with the support of the World Anti Doping Agency, is needed,” an ASO statement noted. “No action can be taken until this process has been completed.”

Riis worried

One interested observer is Bjarne Riis, owner and manager of Saxo Bank, where Contador is slated to race next season in a two-year deal. Riis spoke overnight to Contador’s attorneys and spoke briefly to Contador this morning.

“Of course I’m worried. You know I am. I can’t say much more. I don’t know much more than you do. It’s hard to imagine that this has happened and that he would take this drug. It’s not a drug that makes you ride faster. It’s an old drug that has no effect what so ever, only side effects,” Riis told Danish TV station TV2. “I’ve had the same explanation that he has given everyone else and the same on that he will probably give at the press conference – that it must be caused by something he ate.”